1. Field of the Invention
The present invention relates to an alloy steel powder for high strength sintered parts and particularly to an alloy steel powder which is inexpensive and advantageously develops the high strength as raw material steel powder for sintered machine parts.
2. Description of the Prior Art
As is well known, the applicable field of sintered parts has been broadened owing to the progress of the powder metallurgical technique and therefore an alloy steel powder has been used as raw material powder in addition to pure iron powder. This alloy steel powder is usually produced by water atomization followed by finish-reduction and the development of such an alloy steel powder can firstly provide high strength sintered parts, the production of which has been difficult in the prior process wherein alloy elements are added and mixed with pure iron powder.
The basic requirements for such an alloy steel powder are summarized in the following points:
(1) Raw material powder is inexpensive. PA0 (2) Compressibility is excellent when compacting the parts. PA0 (3) A specific atomsphere is not necessary when sintering the parts. PA0 (4) Mechanical strength of the sintered body is high.
Heretofore, the development of steel powder has been advanced by aiming at the points (3) and (4) among the above described requirements and alloy steel powders, such as 2Ni-0.5Mo, 1.5Ni-0.5Cu-0.5Mo and the like have been proposed. However, these alloy steel powders are relatively high in alloy element amount, so that the cost of the raw material is high and the steel powders become hard. Therefore, such alloy steel powders are not fully satisfactory with respect to the points (1) and (2) among the above described requirements.
The prior alloy steel powders need forging after sintering in most of the cases, that is, should be subjected to so-called "powder forging", therefore in the field where a sintered article is directly used without carrying out the hot compacting, a development of novel alloy has been considered to be necessary.